Grease traps are commonly used to separate greases from the waste water exiting a kitchen. Collecting greases in a grease trap prevents the greases from flowing into the sewer system where the greases may cause problems by congealing in the sewer pipes or interfering with sewage treatment.
Grease traps are commonly installed in restaurant kitchens. In fact, the law in some jurisdictions requires restaurant kitchens to be equipped with grease traps. Such traps are installed in the main drain conduit which carries waste water from the kitchen to the sewer system. The trap separates greases from the waste water leaving the restaurant kitchen and retains the collected greases in a semi-congealed state. Eventually, the trap reaches its capacity, at which point the grease which has accumulated in the trap must be removed and disposed of. If the grease is not removed when the grease trap is full, then the passage of waste water through the trap becomes impeded by excess grease which congeals within the passages inside the trap. This may cause the drains in the restaurant kitchen to back up.
Restaurant kitchen workers typically discover that the chore of removing accumulated grease from a grease trap can be avoided by running hot water through the grease trap. The hot water melts the grease which has congealed within the trap and flushes the grease into the sewer system. This obviously defeats the purpose of the grease trap, which is to prevent grease from entering the sewer system.
The prior art discloses some grease traps which have built-in cooling systems. The main purpose of such cooling systems is apparently to aid in the separation of grease from waste water. Grease tends to separate more easily from cool waste water than from warm waste water. Most grease traps are, therefore, more efficient at removing grease from the waste water stream when the waste water inside the grease trap is cool than they are when the waste water is warm or hot.
Cooled grease traps as disclosed in the prior art may be partially effective to prevent grease which has already accumulated within such traps from being flushed out of such traps by hot waste water. The following are examples of prior art cooled grease traps.
U.S. Pat. No. 1,851,172 Gordon, discloses a grease trap having a cooling jacket for maintaining the inner walls of the grease trap at a low temperature. The cooling jacket may be cooled by means of refrigerating coils within the cooling jacket or by passing cold water through the cooling jacket.
U.S. Pat. No. 1,970,123 Boosey, discloses a grease trap in which a portion of the wall of the grease trap is cooled by cold water flowing in an external circuit.
U.S. Pat. No. 1,977,305 Dehn, discloses another variety of water cooled grease trap having a cooling jacket which is separate from the grease trap itself and which is adapted to be placed in contact with the outside of the grease trap.
A disadvantage of the cooling systems used in these prior art grease traps is that they cannot be retrofitted to previously installed grease traps. They are also expensive to make because they use either expensive refrigerator systems or isolated cold water cooling circuits. Where cold water is used as a coolant, all of these prior art systems take pains to isolate the cold water coolant from the waste water inside the grease trap. This creates complications in plumbing.
U.S. Pat. No. 4,113,617 Bereskin et al. describes a grease trap of particular design in which incoming waste water flows in a thin film through an inlet chamber before passing into the main grease collection chamber of the grease trap. In the inlet chamber the thin film of waste water is cooled by spraying cold water over its surface from multiple overhead spray heads. Waste water from the inlet chamber passes through baffles directly into the grease collection chamber. Further cooling is provided by sucking steam and heated vapours out from above the water in the inlet chamber and grease trap through a fan-forced exhaust manifold.
The cold water spray heads in the Bereskin et al. device are activated by a temperature sensor which is situated downstream from the inlet chamber below the static water level in the grease trap in a pool of water which is permanently retained within the grease trap. Due to the thermal inertia of the water retained in the grease trap the temperature sensor in the Bereskin et al. device cannot react immediately to changes in the temperature of the incoming waste water. Furthermore, because it is downstream from the cooling spray heads the temperature sensor does not sense directly the temperature of the incoming waste water.
The Bereskin et al. grease trap is complicated and therefore relatively expensive to manufacture. It requires a fan-driven exhaust manifold to the outside and an electrical supply to operate optimally which each require installation, possibly by separate tradesmen. The Bereskin et al. grease trap must be relatively large because the inlet chamber must be big enough to allow the incoming waste water to flow in a film. The Bereskin et al. cooling apparatus cannot be retrofitted to an existing grease trap.
A further disadvantage of all of these prior art systems is that no provision is made for cooling waste water before it enters the grease trap. If the waste water is hot and flowing at a high volume then it may not remain in the grease trap long enough to cool down even if the walls of the grease trap are cooled. Therefore, the cooling effect may not be sufficient to prevent accumulated greases from being flushed out of these prior art grease traps by high volume streams of hot waste water.